In the prior art, in semiconductor devices composing semiconductor imaging devices and the like, each optical element having an element region including at least one of a light receiving region and a light emitting region is, for example, a CCD acting as a light receiving element having a light receiving region or an image sensor having a CMOS configuration. For such semiconductor devices, the following configuration has been proposed: a semiconductor element which includes an imaging region having an image sensor formed therein as a light receiving element and includes a plurality of bonding pads is mounted in a recessed cavity formed in a package body, a transparent member is mounted over the cavity, and the transparent member and the package body are secured with a resin adhesive.
In the proposed configuration of the semiconductor device, the semiconductor element is die bonded to a die attachment surface in the cavity of the package body made of ceramic, with a resin such as epoxy resin or a resin sheet. Further, the connecting terminals of the package body and the Al electrodes (bonding pads) of the semiconductor element are electrically connected to each other by wire bonding, and then the cavity is covered with the transparent member. Moreover, the transparent member is fixed on the package body by bonding with a resin adhesive. After that, a protective seal is bonded over the transparent member in order to protect the transparent member during transportation or protect a surface of the transparent member during mounting.
On a surface of the semiconductor element mounted in the semiconductor device configured thus, a plurality of microlenses are formed. Microlenses are called on-chip lenses and are made of acrylic resin which increases a light condensing rate. Such lenses have disadvantages in terms of heat resistance. To be specific, microlenses are softened and deformed by heat applied for a long time. Further, the resin adhesive used for fixing the transparent member to the package body does not have heat resistance.
However, in recent years, there is a growing need for semiconductor devices used with CCDs and image sensors having CMOS configurations under high temperature and humidity conditions. In response to this need, on-chip lens materials and resin adhesives have been improved, so that heat resistance and humidity resistance under high temperature and humidity conditions have been increased for the semiconductor devices and resin adhesives used for the semiconductor devices. Thus the semiconductor devices can be used in such an environment.
Further, the semiconductor device configured thus is mounted on a mounting substrate under high temperature conditions and thus materials resistant to the high temperature conditions during mounting have been demanded. Moreover, when the semiconductor device is mounted on the substrate, a protective seal is necessary for protecting the transparent member from scratches and dust. The protective seal also has to be resistant to heat under the high temperature conditions when the semiconductor device is mounted. Further, it is important to prevent the adhesive of the protective seal from being left on the surface of the transparent member when the protective seal is peeled after passing under the high temperature conditions during mounting.
As a method for preventing the adhesive of a protective seal from being left, for example, Japanese Patent Laid-Open No. 2005-340752 discloses a technique in which a protective seal has a base made of polyethylene naphthalate and is formed by bonding adhesive tapes, each having an adhesive layer at least on one surface. In this technique, it is preferable that the adhesive layer is not provided on a part extended over a light receiving region on a glass surface composing a surface of a video sensor.
In this case, the adhesive layer of the protective seal is not left in the light receiving region on the glass surface but is left in the other regions on the glass surface, so that it is necessary to wipe the glass surface.
However, in the semiconductor device of the prior art, the protective seal is composed of the base made of an organic material and the adhesive layer, and thus when the protective seal is peeled, the outside shape of the protective seal and the adhesive may be left on the surface of the transparent member, that is, on an imaging surface. When the adhesive is left on the imaging surface, the adhesive on the imaging surface may be reflected in an image.
Comparing a heated protective seal and an unheated protective seal, it is found that adhesive is more likely to be left when the protective seal is heated by thermally decomposing the adhesive and the adhesive is more likely to be left when the protective seal is processed under high moisture conditions as compared with the adhesive of the protective seal not processed under high moisture conditions.
Moreover, when the protective seal is bonded to the transparent member, bubbles (voids) may be trapped. In this case, the adhesive is likely to be left around the bubbles.
As a solution to the left adhesive, the surface of the transparent member may be wiped after the protective seal of tape is peeled. In this method, the left adhesive may be spread over the surface of the transparent member during wiping, so that special chemicals have to be used.
Further, when the surface of the transparent member is wiped, dirt or dust left on the transparent member may cause quality defect. Thus wiping has to be carefully performed, which leads to a distinct disadvantage in terms of cost.